Drop and spin test apparatus



July 4, 1967 w. N. STEWART ,3

DROP AND SPIN TEST APPARATUS Filed March 5, 1965' 2 SheetsSheet 1 INVENTOR.

WALTER STEWART VATT Q RN E1 July 4-, 1967 W. N. STEWART DROP AND SPIN TEST APPARATUS 2 Sheets-Sheet 2 Filed March 5, 1965 INVENTOR Direction of Rotaflon ATTORNEYS United States Patent 3,329,014 DROP AND SPIN TEST APPARATUS Waiter N. Stewart, Willingboro, N..l., assignor to the United States of America as represented by the Secretary of the Army Filed Mar. 3, 1965, Ser. No. 436,968 7 Claims. (Cl. 73-167) ABSTRACT OF THE DISCLOSURE A drop and spin test apparatus for a mechanical time fuze requiring a set-back force and/ or spin for actuation of the timer movement by which the point of initiation of an armed fuze may be determined in a safe manner. Preferably, a drop tube overlies an enclosed rotatable impact surface which is provided with means for locking or securing thereto the fuze in a predetermined centrally oriented position.

The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon,

This invention relates to a drop and spin test apparatus, and particularly to an apparatus for applying drop and spin tests to a mechanical time fuze.

In general the operation of a mechanical time fuze used with a large caliber gun-fired round of ammunition depends on the initial impact force necessary for propelling the round and the centrifugal force imparted to the components of the fuze from the spinning of the round while in flight. A typical mechanical time fuze contains a setback pin which essentially holds the timing mechanical in an inactive state. The setback pin is arranged to be dislodged when a certain impact force is imparted to the fuze. At this point the timing mechanism is free to respond to the spinning of the fuze. After a known number of spinning revolutions is reached the fuze is activated, that is, the timer movement starts to run and when a preset time is reached the detonator is initiated to fire the round.

In order to insure proper functioning of these mechanical time fuzes tests simulating actual operating conditions are conducted. Fuzes are selected from specific lots and are subjected to an impact or drop test to ascertain whether the setback pin is dislodged at the proper design force. The active fuze (i.e. setback pin dislodged) is then given a spin test to determine whether the fuze will detonate at the predetermined design revolution thereof. Occasionally older fuzes are sent back from the field to be tested to insure that they are still useful, or a fuze lot is returned because of suspected malfunctioning. In all situations the test procedure is the same. Previously the drop test and spin test were performed in separate apparatus. This created a safety hazard in that a live fuze had to be transported from the drop test apparatus to the spin test apparatus. A situation could and did arise where malfunctioning fuzes would fire when handled immediately after drop test.

Accordingly, it is an object of the present invention to provide an apparatus for applying drop and spin tests to a mechanical time fuze, which apparatus enables the determination of a point of initiation of a test fuze in a safe manner without the necessity of multiple handling of the test fuze detonator.

It is another object of the present invention to provide a drop and spin test apparatus which enables the drop test of a mechanical time fuze to be conducted safely without removal of the fuze detonator.

It is still another object of the present invention to provide a drop and spin test apparatus which combines a drop tube with an enclosed rotatable impact surface for fulfilling the drop test requirement and a means for aligning the test fuze with the impact surface while simultaneously locking the test fuze in place and finally rotating the impact surface and test fuze by suitable means for fulfilling the spin test requirement.

Further features, objects and advantages will either be specifically pointed out or become apparent when for a better understanding of the invention reference is made to the following written description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a front elevation view partly in cross section of an apparatus illustrating a preferred embodiment of the present invention;

FIG. 2 is a view of an alternative element which may be used with the present invention;

FIG. 3 is a front elevation view of the apparatus of FIG. 1 showing further details of construction.

Referring to the drawings wherein like reference characters refer to like parts throughout 10 is a support frame or mounting plate upon which is situated an upright enclosure 12 or explosion chamber, suitably adapted and of suflicient strength to contain the explosion of a mechanical time fuze detonator. The enclosure 12 is secured to the support frame 10 by welding or the like. An opening 14 is provided in the upper end portion of the enclosure 12. Directly below the opening 14 of the enclosure 12 is a bed 16 of thick metal construction. This bed 16 is oriented in a horizontal lane and has its center point coaxial with the opening 14. In this embodiment the bed 1 6 is the base portion of a three jaw chuck 18. The function of this chuck 18 will be described later on in this specification. A soft metal pad 21) is disposed on the bed 16 coaxially with the center point thereof. The pad 20 may be composed of a metal such as lead antimony and this pad 20 along with the bed 16 serves as an impact surface for test fuze.

A vertical shaft 22 is integrally fixed to the lower portion of the bed 16. Actually the shaft 22 is fixed to the chuck 18 but for reasons ofclarifying this description the inter-relationship of the elements hereafter described will be referred to the bed 16. The shaft 22 and bed 16 are rotatably supported within the enclosure 12 by bearing assemblies 24, 26 and 28. The bearing assembly 24 is a combination ball or roller radial bearing 30 and radial upper and lower flange bearings 32 and 34. The upper flange bearing 32 is in mating relationship with the shaft 22 mounted ball bearing 30 both of which are supported by the upper surface of a bulkhead 36 which is disposed in the enclosure 12 and fixed by suitable means to the inner wall thereof. The lower {flange bearing 34 is fixed to the lower surface of the bulkhead 36 by means of a plurality of bolts 38 passing through communicating threaded openings in the lower flange bearing 34, the bulkhead 36 and the upper flange bearing 32. The bearing assembly 26 is positioned below the bearing assembly 24 and is comprised of upper and lower flange bearings 40 and 42 supported by a bulkhead 44 fixedly disposed in the enclosure 12 by suitable means. Bolts 38 or the like secure the flange bearings 40 and 42 to each other and to the bulkhead 44 as shown. The bearing assembly 28 comprises a single flange bearing 46 fixed by bolts 48 or the like to the support frame 10.

A variable speed motor 50 is fixedly mounted to the outside surface of the enclosure 12. The motor 50 has an external speed changer 52 which includes an indicator 54 for readily ascertaining the motors speed of rotation. Since a projectile fired through a rifled gun barrel is given a rapid rotational acceleration it is preferable that the motor 50 be of a type which has the capability of accelerating to a preset speed in rapid order measured in microseconds. The rotor 56 of the motor 50 has an integrally mounted pulley 58 or the like thereon. This pulley 58 is coplanar with another pulley 60 fixedly mounted on the shaft 22. The pulleys 58 and 60 are interconnected with each other by a belt 62 suitable for this purpose. By the above arrangement of elements it is readily seen that the motor 50 and bed 16 are operatively connected so that the motor 50 may drive the bed 16 to a preselected speed. The motor 50 is connected with a suitable electrical power source, not shown.

A drop tube 64 is fixed to the upper surface of the enclosure 12 and is coaxially arranged with the enclosure 12 opening 14. As described previously, the opening 14 is coaxial with the center point of the bed 16, thus, the drop tube 64 is, likewise, coaxial with the center point of the bed 16. The drop tube 64 is made to extend to a vertical height above the bed such that when a test fuze is dropped down the tube 64 it will strike the pad 20 (i.e., the bed 16) with a predetermined impact force. This vertical height above the bed 16 is defined in this specification as the effective height of the drop tube 64.

The three jaw chuck 18 previously mentioned enables the alignment of a test fuze with the bed 16 while substantially simultaneously locking it to the bed 16. In this embodiment the jaws 66 of the chuck 18 are operatively connected with each other in familiar fashion to be simultaneously moved when desired. The jaws 66 may be operated manually by a socket wrench 68 suitably inserted in a complementary screw 70 in the chuck 18 which in turn cooperates with the familiar internal elements of the common three jaw chuck 18 which this represents. The wrench 68 extends through a passageway in the side of the enclosure 12. The wrench 68 is held in alignment with the screw 70 by means of a bushing 72 securely fixed in the passageway provided. A helical coil spring 74 urges a force on the wrench 68 outwardly from the enclosure 12. This prevents the wrench from inadvertently remaining in the screw 70 when the bed 16 is to be rotated. A thumb screw 76 extends through a threaded radial opening in the bushing 72 wall to communicate with the wrench 68 body. The thumb screw 76 may be tightened to fix the wrench 68 in the screw 70 to aid in holding the bed 16 stationary when a drop test is to be performed.

FIG. 2 illustrates an automatic chuck 78 which can be used in place of the three jaw chuck 18. The chuck 78 is a self centering and aligning chuck. The jaws 80 are normally spring urged outwardly as shown by the phantom outlines. When the bed 16 is rotated centrifugal force acts against the springs 82 to pivot the jaws 80 inwardly as shown by solid line representation in FIG. 2. A test fuze will remain locked and centered so long as a certain minimum speed of the bed 16 is maintained.

FIG. 3 shows the enclosure 12 adapted to have its upper end portion pivotably opened. The upper end portion 84 is hinge mounted at 86 to the lower portion 87. A lock 88 is provided between the upper and lower portions for securing same to each other during operation of this test apparatus. A window 90 of safety glass may be provided on the upper portion 84 of the enclosure 12 for observing the operation within.

In operation a test fuze 92 to be tested is inserted in a suitable fuze holder 94. The fuze holder 94 is then placed in the drop tube 64 and released. The drop tube 64 guides the fuze 92 and fuze holder 94 to the bed 16. The force of gravity acts to increase the momentum of the fuze 92 and fuze holder 94 until the bed 16 is reached when the desired impact force is thus imparted to the test fuze 92. At this point the setback pin should be released and the fuze rendered active (i.e., the timing mechanism is set to operate). While the drop test was being conducted the bed 16 was held in place by the wrench 68 fixed in the screw 70 by the tightening of the thumb screw 76 against the wrench 68 body. With the fuze 92 and fuze holder 94 on the bed 16 the thumb screw is released and the three jaw and chuck 18 tightened by turning the wrench 68. The fuze holder 94 is thereby aligned with the center point of the bed 16 while at the same time being locked in fixed relationship therewith. Using the automatic chuck 78 of FIG. 2 would, of course, obviate this manual tightening aligning and locking procedure.

With the fuze holder 94 aligned and locked in place the motor 50 is turned on and the preselected speed achieved by rapid acceleration. When the detonator of the fuze is initiated the time at which this firing takes place is recorded. This data is accordingly compared with the design data to determine whether the fuze 92 is operated as was desired. The upper portion 84 may now be unlocked and pivoted open to remove the fuze holder 94. The upper portion 84 may then be returned to its initial position, locked, and testing of another fuze commenced.

Resort may be had to the various modifications and variations which fall within the spirit of the invention and the scope of the appended claims.

I claim:

1. An apparatus for applying drop and spin tests to a mechanical time fuze, including means defining a flat solid bed for use as an impact surface; means operatively connected with said bed means for rotating same;

enclosure means surrounding said bed means and having an opening therein overlying said bed means;

guide means above said bed means for directing a test fuze under the force of gravity onto said bed means, said guide means having its terminus substantially axially aligned with the center point of said bed means, said guide means having an effective vertical height above said bed means such that a desired impact force may be imparted to a test fuze upon free fall from said height to the surface of said bed means; and

means on said bed means for substantially simultaneously axially aligning a test fuze with said bed means center point and locking the test fuze in fixed relationship with said bed means.

2. An apparatus for applying drop and spin tests to a mechanical time fuze, including means defining a fiat solid bed for use as an impact surface; enclosure means surrounding said bed means and adapted for containing the detonation explosion of a test fuze, said enclosure means defining an opening above said bed means and axially aligned with the center point thereof; guide means above said bed means for directing a test fuze under the force of gravity onto said bed means, said guide means having its terminus substantially coaxial with said enclosure means opening, said guide means having an effective vertical height above said bed means such that a desired impact force may be imparted to a test fuze upon free fall from said height to the surface of said bed means; means without said enclosure means operatively connected with said bed means for rotating same; and

means on said bed means for substantially simultaneously axially aligning a test fuze with said bed means center point and locking the test fuze in fixed relationship with said bed means.

3. An apparatus for applying drop and spin tests to a mechanical time fuze, including means defining a flat solid bed for use as an impact surface, said bed means positioned in a substantially horizontal plane;

enclosure means surrounding said bed means and adapted for containing the detonation explosion of a test fuze, said enclosure means defining an opening above said bed means and axially aligned with the center point thereof;

vertical guide means above said bed means for directing a test fuze under the force of gravity onto said bed means, said guide means substantially coaxial with said enclosure means opening, and having a vertical height above said bed means such that a desired impact force may be imparted to a test fuze upon free fall from said height to the surface of said bed means;

means without said enclosure means operatively connected with said bed means for rotating same; and

means on said bed means for substantially simultaneously axially aligning a test fuze with said bed means center point and locking the test fuze in fixed relationship with said bed means.

4. An apparatus for applying drop and spin tests to a mechanical time fuze, including a support frame;

an enclosure mounted on said frame and adapted to contain the detonation explosion of a test fuze, said enclosure defining an opening through its upper end surface;

a flat solid bed for use as an impact surface and positioned in a substantially horizontal plane with its center point substantially axially aligned with said enclosure opening;

a vertical rotatable shaft operatively connected with said bed;

means within said enclosure for rotatably supporting said shaft;

means without said enclosure, and supported thereon,

6 operatively connected with said shaft for rotating said shaft and said bed;

.a vertical drop tube above said bed, said drop tube having its lower end fixed to said enclosure in a substantially coaxial relationship with said enclosure opening, said drop tube having a vertical'height above said bed such that a desired impact force may be imparted to a test fuze upon free fall from said height to the surface of said bed; and

means on said bed for substantially simultaneously axially aligning a test fuze with said bed center point and locking the test fuze in fixed relationship with said bed.

5. An apparatus as defined in claim 4 wherein said aligning and locking means is a three jaw chuck, each jaw operatively connected with each other to substantially simultaneously move inwardly towards the center point of said bed to align and lock a test fuze to said bed.

6. An apparatus as defined in claim 4 wherein said enclosure is provided with a removable cover on its upper end portion, said cover further defining a window for viewing of the interior of said enclosure.

7. An apparatus as defined in claim 4 wherein said aligning and locking means is so constructed and arranged that it may. be operated from without said enclosure means.

References Cited UNITED STATES PATENTS 2,981,093 4/1961 Rhea 73-35 3,065,626 11/ 1962 Westerman 73-5 DAVID SCHONBERG, Primary Examiner. 

1. AN APPARATUS FOR APPLYING DROP AND SPIN TESTS TO A MECHANICAL TIME FUZE, INCLUDING MEANS DEFINING A FLAT SOLID BED FOR USE AS AN IMPACT SURFACE; MEANS OPERATIVELY CONNECTED WITH SAID BED MEANS FOR ROTATING SAME; ENCLOSURE MEANS SURROUNDING SAID BED MEANS AND HAVING AN OPENING THEREIN OVERLYING SAID BED MEANS; GUIDE MEANS ABOVE SAID BED MEANS FOR DIRECTING A TEST FUZE UNDER THE FORCE OF GRAVITY ONTO SAID BED MEANS; SAID GUIDE MEANS HAVING ITS TERMINUS SUBSTANTIALLY AXIALLY ALIGNED WITH THE CENTER POINT OF SAID BED MEANS, SAID GUIDE MEANS HAVING AN EFFECTIVE VERTICAL HEIGHT ABOVE SAID BED MEANS SUCH THAT A DESIRED IMPACT FORCE MAY BE IMPARTED TO A TEST FUZE UPON FREE FALL FROM SAID HEIGHT TO THE SURFACE OF SAID BED MEANS; AND MEANS ON SAID BED MEANS FOR SUBSTANTIALLY SIMULTANEOUSLY AXIALLY ALIGNING A TEST FUZE WITH SAID BED MEANS CENTER POINT AND LOCKING THE TEST FUZE IN FIXED RELATIONSHIP WITH SAID BED MEANS. 